This invention relates to dynamoelectric machines with a radial path, air cooled rotor and particularly to means for improving coolant flow therethrough.
The subject matter of commonly assigned applications Ser. No. 552,592, filed Nov. 16, 1983, by Pavlik et al., now U.S. Pat. No. 4,508,985, and Ser. No. 607,854, filed of even date herewith by Hammer et al. is incorporated herein by reference.
In the earlier copending application are described the general characteristics of machines with radial path air cooled rotors as they have been made heretofore and an improvement thereto for providing better flow into slot channels by means of a channel inlet fairing. This provides better cooling of the rotor so that machine size and noise can be reduced. The present invention has to do with machines of the same general character but with another aspect for improving coolant flow and reducing machine size and noise.
In addition, the above-mentioned second application relates to other features for similar purposes. It is advantageous to employ the features of the above-mentioned applications, either individually or together, with those of the present invention. However, any of such features may be individually used to improve the cooling of machines.
In machines with radial air cooling of the rotor in accordance with the prior art, the air flows radially inward through a stationary inlet duct to the retaining ring and field winding end turns. Part of the air flows axially and radially outward, cooling the end turns and then exiting through the retaining ring. The remaining air passes into the field winding subslots, and hence radially outward through a number of slits in the field winding, cooling the body portion of the winding. The air then exits through radial holes in the rotor wedges and enters the air gap. The air from the body portion of the winding flows axially and circumferentially along the air gap and joins the air from the end turn portion of the winding. This combined exhaust flow then exits through the enclosure to a cooler where heat is removed and the air recirculated.
In such machines, the rotor itself is a blower which must produce the required pressure-volume characteristics to obtain the desired flow. If the rotor is unable to meet the requirements for air flow, prior practice has dictated that rotor mounted blowers be employed, necessarily and disadvantageously increasing the machine weight and size, airborne noise levels, and power consumption.
The present invention offers a means to approximately double the available driving differential static pressure produced by the rotor as compared to an otherwise like machine.
The air flow path is improved by adding a smooth arcuate shell structure, preferably made of insulating material, to the stator end turns and to similarly curve the configuration of a portion of the exhaust side of the inlet duct to form a diffuser for the exhaust gas from the retaining ring and air gap. The diffuser also serves as a noise baffle.
The shell structure around the stator end turns prevents air from impinging thereon and means that the coolant gas dynamic pressure resulting from rotor rotation is converted into useful static pressure utilized to induce the required gas flow without additional total temperature rise in the cooling gas. Also, noise generated by air chopping or modulation caused by gas jets flowing from the retaining ring vent holes and impinging upon the stator end turns is eliminated by the stator end turn shell structure which provides a smooth continuous surface.
In a specific embodiment of preferred design, the stator of the machine is one that is of a high power density design, such as with water cooled windings, which requires little cooling gas for the stationary generator components. Hence, the rotor exhaust gas consists of substantially all the originally supplied air to the rotor.
In preferred forms, the combination including the exhaust gas diffuser and noise baffle in accordance with this invention is combined with prewhirl vanes in the inlet duct, a subslot inlet fairing, and with variably dimensioned wedge openings in the slot portion of the machine so as to result in greater overall improvement.